popen issues

[Hal Fulton]

Here's something I've never figured out.

Suppose I want real two-way communication with a process via popen.
This seems doable.

But apparently the read hangs until I do a close_write; and if I
do that, I can't write again. A flush doesn't work.

Here's what I was thinking (simplified):

io = IO.popen("/bin/bash","r+") do |f|
f.puts "ls"
puts f.readlines
f.puts "date"
puts f.readlines
end

I even tried this (following) abomination, to no avail:

io = IO.popen("/bin/bash","r+") do |f|
writer = f.dup
f.puts "ls\n"
f.close_write
puts f.readlines
w = writer.dup
w.puts "date\n"
w.close_write
puts f.readlines
end


Can someone advise?


Hal

 

[Ara.T.Howard]

Here's something I've never figured out.

Suppose I want real two-way communication with a process via popen.
This seems doable.

But apparently the read hangs until I do a close_write; and if I
do that, I can't write again. A flush doesn't work.

Here's what I was thinking (simplified):

io = IO.popen("/bin/bash","r+") do |f|
f.puts "ls"
puts f.readlines
f.puts "date"
puts f.readlines
end

I even tried this (following) abomination, to no avail:

io = IO.popen("/bin/bash","r+") do |f|
writer = f.dup
f.puts "ls\n"
f.close_write
puts f.readlines
w = writer.dup
w.puts "date\n"
w.close_write
puts f.readlines
end


Can someone advise?


Hal

~/tmp > ls
b.rb


~/tmp > cat b.rb
require 'session'
bash = Session::Bash.new

puts '---'
cmd = 'ls'
p cmd
o,e = bash.execute cmd
p o
p e


puts '---'
cmd = 'date'
p cmd
bash.execute(cmd) do |o,e|
o and p o
e and p e
end

puts '---'
cmd = 'find'
bash.errproc = lambda{|e| p e}
bash.outproc = lambda{|o| p o}
bash.execute cmd


~/tmp > ruby b.rb
---
"ls"
"b.rb\n"
""
---
"date"
"Tue Apr 27 15:40:21 MDT 2004\n"
---
".\n"
"./b.rb\n"



it's horribly more complex than it first appears. read the source to see why (RAA)

- you don't know whey the output of one command starts and the next begins
- you can't to non-blocking reads from threads
- you can't send commands w/o blocking entire processs unless carefull

i believe my package is thread safe - as in it doesn't block them, not as in
many can use a session at once. at least i using it for many multi-threaded
apps.

this took my over a week to write - you may want to save the trouble - the
source is really straight forward to read. (IMHO)

-a
--
===============================================================================
| EMAIL :: Ara [dot] T [dot] Howard [at] noaa [dot] gov
| PHONE :: 303.497.6469
| ADDRESS :: E/GC2 325 Broadway, Boulder, CO 80305-3328
| URL :: http://www.ngdc.noaa.gov/stp/
| TRY :: for l in ruby perl;do $l -e "print \"\x3a\x2d\x29\x0a\"";done
===============================================================================

 

[Hal Fulton]

Ara.T.Howard wrote:

[snip]

it's horribly more complex than it first appears. read the source to see why (RAA)

- you don't know whey the output of one command starts and the next begins
- you can't to non-blocking reads from threads
- you can't send commands w/o blocking entire processs unless carefull

i believe my package is thread safe - as in it doesn't block them, not as in
many can use a session at once. at least i using it for many multi-threaded
apps.

this took my over a week to write - you may want to save the trouble - the
source is really straight forward to read. (IMHO)

Very cool, Ara, thanks. I'll take a look at it.

Hal

 

[Kristof Bastiaensen]

Here's something I've never figured out.

Suppose I want real two-way communication with a process via popen.
This seems doable.

But apparently the read hangs until I do a close_write; and if I
do that, I can't write again. A flush doesn't work.

Hi,

I don't know how to do it in pure Ruby, but if you are
using a GUI (Gtk) it is fairly easy.

pipe = IO.popen("prog", "w+")
Gtk::input_add(pipe.to_i, Gdk::INPUT_READ) {
str = pipe.gets
puts "got " + str }

This will work only from the event-dispatch routine inside
Gtk.main().

Kristof

 

[Kristof Bastiaensen]

Hi,

It is maybe not a good idea to use /bin/bash as a pipe,
because it is an interactive interpreter, and not made
for pipe-communication. Normally you would just check
for an end of file byte, but bash will not send you
one. Is there any reason to use bash?

 

[Ara.T.Howard]

Hi,

It is maybe not a good idea to use /bin/bash as a pipe, because it is an
interactive interpreter, and not made for pipe-communication. Normally you
would just check for an end of file byte, but bash will not send you one.
Is there any reason to use bash?

really? mine does:

~ > ruby -e 'p IO.popen("bash -c exit").eof?'
true

~ > uname -srm && bash --version
uname -srm && bash --version
Linux 2.4.20-30.73ncirt i686
GNU bash, version 2.05a.0(1)-release (i686-pc-linux-gnu)
Copyright 2001 Free Software Foundation, Inc.

how about you?

-a

--
===============================================================================
| EMAIL :: Ara [dot] T [dot] Howard [at] noaa [dot] gov
| PHONE :: 303.497.6469
| ADDRESS :: E/GC2 325 Broadway, Boulder, CO 80305-3328
| URL :: http://www.ngdc.noaa.gov/stp/
| TRY :: for l in ruby perl;do $l -e "print \"\x3a\x2d\x29\x0a\"";done
===============================================================================

 

[Kristof Bastiaensen]

really? mine does:

~ > ruby -e 'p IO.popen("bash -c exit").eof?'
true


how about you?

Indeed, if you call bash with an argument it does.
But if you call just bash, like in the previous example, it
doesn't. Instead of IO.popen("/bin/bash -c command"),
you could better do just IO.popen("command"), (unless of
course you want bash specific features).

Kristof

 

[nobu.nokada]

Hi,

At Wed, 28 Apr 2004 06:06:30 +0900,
Hal Fulton wrote in [ruby-talk:98572]:

Here's what I was thinking (simplified):

io = IO.popen("/bin/bash","r+") do |f|
f.puts "ls"
puts f.readlines

IO#readlines reads all of the lines, i.e., blocks until the all
child processes exit or close the stdout. You probably can use
sysread instead, and IO#readpartial proposed by akr (see
[ruby-talk:96220]) would help you if it is implemented.

 

[Hal Fulton]

Indeed, if you call bash with an argument it does.
But if you call just bash, like in the previous example, it
doesn't. Instead of IO.popen("/bin/bash -c command"),
you could better do just IO.popen("command"), (unless of
course you want bash specific features).

In my example, I was just using bash as an interactive
program.

Actually I tried bc first, with similarly no luck.

It's not a question about bash or bc, but about popen.


Hal

 

[Hal Fulton]

Hi,

At Wed, 28 Apr 2004 06:06:30 +0900,
Hal Fulton wrote in [ruby-talk:98572]:

Here's what I was thinking (simplified):

io = IO.popen("/bin/bash","r+") do |f|
f.puts "ls"
puts f.readlines

IO#readlines reads all of the lines, i.e., blocks until the all
child processes exit or close the stdout. You probably can use
sysread instead, and IO#readpartial proposed by akr (see
[ruby-talk:96220]) would help you if it is implemented.

Of course, this makes sense. Thank you.

I don't remember #readpartial but I will read about it.

Thanks,
Hal

 

[Dan Janowski]

I think putting the process in a pty will give you better control.

Dan

 

[Ara.T.Howard]

I think putting the process in a pty will give you better control.

Dan

dan-

have you seen my session package? do you think i should re-vamp this to run
all processes in a pty? i can't think of a good reason NOT to at this point,
but aren't currently...

-a

--
===============================================================================
| EMAIL :: Ara [dot] T [dot] Howard [at] noaa [dot] gov
| PHONE :: 303.497.6469
| ADDRESS :: E/GC2 325 Broadway, Boulder, CO 80305-3328
| URL :: http://www.ngdc.noaa.gov/stp/
| TRY :: for l in ruby perl;do $l -e "print \"\x3a\x2d\x29\x0a\"";done
===============================================================================

 

[Dan Janowski]

a-

I have not seen your session package (nose too close to grind stone at
the moment). I would not use ptys if you have code control over the
child, since any behavior issues can be worked out. In most other
cases, a pty has lots of advantages: stdio buffering turned off, good
process control since the master is effectively the controlling
terminal, no intermediate shell, etc. I would guess that character
throughput is less than with popen because of the pty stack, but I
could not tell you how much or if it matters.

-d

I think putting the process in a pty will give you better control.

Dan

dan-

have you seen my session package? do you think i should re-vamp this
to run
all processes in a pty? i can't think of a good reason NOT to at this
point,
but aren't currently...

-a

--
=======================================================================
========
| EMAIL :: Ara [dot] T [dot] Howard [at] noaa [dot] gov
| PHONE :: 303.497.6469
| ADDRESS :: E/GC2 325 Broadway, Boulder, CO 80305-3328
| URL :: http://www.ngdc.noaa.gov/stp/
| TRY :: for l in ruby perl;do $l -e "print
\"\x3a\x2d\x29\x0a\"";done
=======================================================================
========